Protective Silica Coatings on Zinc-Sulfide-Based Phosphor Particles

A spray drying approach was used to apply 15-nm-thick SiO₂ continuous coatings onto ZnS:Ag phosphor particles. A prehydrolyzed TEOS dip coating formula was used as the SiO₂ precursor. The phosphor was mixed together with the precursor then atomized without allowing gelation to occur until the droplets containing the particles were in flight. The coating gelled and dried while falling through a graded heat zone. The dried coated particles were captured in a cyclone separator and heat-treated to further densify the SiO₂ coating. The coatings protected the phosphors while in service in field emission display (FED) devices.